Syrian forces shot dead at least 13 civilians on Sunday in a continued military assault on the restive city of Homs and in attacks on pro-democracy demonstrations that erupted after prayers marking the main Muslim feast, activists said.

Qatar's prime minister called for Arab states to meet next Saturday to discuss Syria's failure to implement a deal struck with the Arab League to end bloodshed that was touched off by the popular uprising against president Bashar al-Assad.

The official Egyptian news agency, MENA, said the gathering would address "the continuing violence and the government's failure to stick to its obligations under the Arab Action Plan to solve the crisis in Syria".

Arab leaders have ramped up criticism of Assad as the killings mounted, but have shied away from demanding major political change in the country for fear chaos could ensue, given Syria's volatile sectarian divisions.

Syria is dominated by Assad's minority Alawite sect, while Sunni Muslims form the majority.

Damascus has described growing Arab criticism as unproductive and based on false media reports.

It says the unrest has arisen largely from a foreign conspiracy to divide Syria and that security forces are using legitimate means to confront "terrorists" and Islamist militants bent on wrecking a reform drive by Mr Assad.

Opposition leaders say the protests are driven by broad discontent with a corrupt repressive elite, not by violent extremists, and that Mr Assad's promises of reform have been discredited by his continuing military crackdown on protesters.

The official Syrian news agency said Mr Assad went to the eastern provincial capital of Raqqa on Sunday where he joined Eid prayers with "a number of notables and popular, union and party organisations and a crowd of Raqqa citizens".

"The stand Syrians are making against terrorism and outside intervention is the basis for Syria's steadfastness," the SANA agency quoted Assad as saying.

No let-up

Most of the deaths on Sunday occurred in Homs, 140 km north of Damascus, where a main district has been under tank bombardment since Tuesday, the day before Syrian authorities agreed in Cairo to the Arab League initiative.

Under the deal, the army was supposed to pull out of turbulent cities, political prisoners would go free, and talks with the opposition would begin within two weeks.

A demonstrator was shot dead when security police fired at a protest in Hama, north of Homs, demanding the removal of Assad, and three were killed in the north-western province of Idlib, said the activist Syrian Revolution General Commission.

The organisation said in a statement that at least 10 protesters were injured in the town of Talbisah near Homs and in Harra in the Hauran Plain in Syria's south.

Fifty protesters were arrested after a demonstration in the Damascus district of Kfrar Souseh. Troops and militiamen loyal to Assad deployed in several Damascus suburbs, surrounding mosques to prevent crowds from rallying after the early morning prayers for the feast of Eid al-Adha, the commission said.

"Idlib saw big demonstrations across its towns and villages this morning," local activist Raed Ayham said by phone.

"There is disillusionment that the Arab League agreement has failed to curb the repression.

"The army is escalating the crackdown in the hope of wrapping this uprising up before the Arabs take more steps against the regime. Assad has not understood that the killings are only feeding the opposition against him."

Syrian authorities have banned most non-official media since the revolt against 41 years of rule by the Assad family and their Baath Party erupted in March, making independent verification of events difficult.

Activists and residents said tank fire killed at least 13 civilians and wounded dozens in Homs on Saturday. The day before, security forces killed at least 19 people and wounded dozens across Syria, mostly in shootings at protests.

Deaths denied

State media denied any protesters had been killed on Friday.

The official Syrian news agency, SANA, quoted the provincial governor as saying the authorities were "serious" about implementing an amnesty announced last week to anyone with weapons if they were not involved in killings.

He said four soldiers and police, including two from Homs, killed in violence were buried on Sunday.

The authorities say Islamist militants and foreign-backed armed gangs have killed 1,100 members of the security forces during the uprising.

The United Nations says more than 3,000 people have been killed in Mr Assad's crackdown.

In Cairo on Saturday, the head of the Arab League said it was seriously concerned by the violence in Syria, and appealed to Damascus to abide by steps agreed with Arab states to protect civilians and set Syria on a course of political dialogue.